testing-coverage-requirements.md

---

title: Maintain 80%+ Test Coverage for New Code impact: HIGH impactDescription: Prevents bugs and enables confident refactoring tags: testing, coverage, quality

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Maintain 80%+ Test Coverage for New Code

Impact: HIGH

Every PR must have near-80%+ test coverage for the code it introduces or modifies. If you add 50 lines of new code, those 50 lines must be covered by tests.

What to Test

Example

// item.service.spec.ts
describe('ItemService', () => {
  let service: ItemService;
  let repo: jest.Mocked<ItemRepository>;

  beforeEach(async () => {
    const module = await Test.createTestingModule({
      providers: [
        ItemService,
        { provide: ItemRepository, useValue: createMock<ItemRepository>() },
      ],
    }).compile();

    service = module.get(ItemService);
    repo = module.get(ItemRepository);
  });

  describe('findBySlug', () => {
    it('returns item when found', async () => {
      const mockItem = { id: '1', name: 'Test', slug: 'test' };
      repo.findBySlug.mockResolvedValue(mockItem);

      const result = await service.findBySlug('test');
      expect(result).toEqual(mockItem);
    });

    it('returns null when not found', async () => {
      repo.findBySlug.mockResolvedValue(null);

      const result = await service.findBySlug('nonexistent');
      expect(result).toBeNull();
    });
  });
});

Rules

• Services must have unit tests with mocked dependencies
• Use AI assistance to generate comprehensive test suites
• Test edge cases: empty inputs, invalid data, boundary conditions
• Test error paths: what happens when things go wrong